<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>js</title>

    <script>

        // var a=2.5;
        // var str='hello'+a.toString();
        var str='If you purchase more than 100 sets, the price of product A is $9.90.';
        // alert(str.substring(2,3));
        // alert(str.charAt(5));
        // alert(str.indexOf('lr'));
        // alert(str.slice(1,-1));
        var reg=/\d+/;
        alert(reg.exec(str)+reg.exec(str));



    </script>
</head>
<body>



</body>
</html>